The present invention relates to microbial decontamination arts. It finds particular application in conjunction with powdered sterilant concentrates which react in room temperature water to form microcidally active compositions with an extended period of active life for field medical use and will be described with particular reference thereto. It is to be appreciated that the invention will also find application in conjunction with other anti-microbial applications including biocidal compositions for use at elevated temperatures, biocidal compositions with other preselectable active durations, and the like.
Our earlier U.S. Letters Pat. No. 5,116,575 describes a powdered anti-microbial composition which is ideally suited for use in automated liquid sterilization systems such as illustrated in the above-referenced U.S. Pat. No. 4,892,706 or 5,217,698. The anti-microbial composition included two components which reacted in the presence of water to form a strong oxidant- Preferably, acetylsalicylic acid and a perborate, such as sodium perborate, reacted to form peracetic acid. The powdered components further included anti-corrosive materials and buffers. The anti-corrosive materials inhibited corrosion of brass, copper, aluminum, steel, and other materials commonly found in medical, dental, and surgical instruments. The buffers controlled the chemical reaction and assisted in the corrosion inhibition. In particular, the preferred composition was formulated for optimum efficiency at 50.degree. C. and to produce and maintain a peak peracetic acid concentration for the duration of the automated cycle, on the order of 1/2 hour.
Although the prior formulations were effective for their intended purpose, there is also a need for an anti-microbial formulation which reacts quickly in room temperature water, about 25.degree. C., to produce an anti-microbially active solution for an extended period, on the order of eight hours. Such formulation should also inhibit corrosion and buffer pH to an optimal range.
An article by Death and Coates in the Journal of Clinical Pathology, Vol. 32, pp. 148-153 (1979) entitled "Effective pH on Sporicidal and Microbicidal Activity of Buffered Mixtures of Alcohol and Sodium Hypochlorite" noted superior microbicidal activity in a methanol/hypochlorite mixture and hypochlorite alone when buffered to a pH of about 7.6-8.1. An article by Melichercikova in the Journal of Hygiene, Epidemiology, Microbiology, and Immunology, Vol. 33, No. 1, pp. 19-28 (1989) entitled "Disinfectant Effect of Persteril in Combination With Detergents" investigated shelf life of Perstil stabilized peracetic acid aqueous solutions. They proposed that peracetic acid should not be applied in combination with basic detergents because the sporicidal effect of peracetic acid was markedly declined at a pH of 9. In a paper by Hauthal, et al. in Tenside Surf. Det., Vol. 27, No. 3, pp. 187-193, entitled "Studies Concerning the Mechanism of Bleaching Activation", the effects of pH on bleaching activators diacetyl dioxohexahydrotriazine (DADHT) and tetraacetyl ethylene-diamine (TAED) in the formation of peroxyacetic acid with hydrogen peroxide or sodium perborate is investigated. This article notes that at higher pH values, the rate of peroxyacetic acid formation increases but becomes unstable, decomposing more rapidly to oxygen and acetic acid.
Although these references address the effects of pH, none teach or fairly suggest an appropriate powdered formulation which mixes in room temperature water to form microcidally effective concentrations of peracetic acid rapidly but whose stability is sufficiently high that microbicidal activity for a period of at least eight hours is assured. The present invention provides a new and improved sterilant formulation which overcomes the abovereferenced problems and others.